Trip-free circuit breaker



Oct. 7, 1952 M. B. wooD TRIP-FREE CIRCUIT BREAKER Filed June 24, 1949 w ull INVENTOR MORRIS B. WOOD By his Atorney Patented Oct. 7, 1952 UNITED STATES PATENT OFFICE TRIP-'FREE CIRCUIT BREAKER Morris B. Wood, Newburyport, Mass.

Application June 24, 1949, SerialNo. 101,013

14 Claims.

The present invention relates to electrical .circuit breakers, .particularly of the trip free type and is herein illustrated as embodied :in a compact and easily assembled'form `which automatically .resets itself in readiness for reclosing after having opened'its circuit upon the occurrenceof overload conditions.

.An lobject o f the invention is to provide a trip free overload circuit breaker vof vimproved construction and form capable of .being constructed inexpensively andof operating reliably and with good durability under Va, wide range of .operating conditions. Ano-ther object is to pro-vide a circuit breaker of the trip free type which will reset itself automatically for reclosing andwhich may vthen be reclosed vand reopened repeatedly under .overloadv conditions. A still yfurther object is to providea circuit breaker of the type referred to 4with a simply actuated, manual .operating connection and at the same time to provide .a quick closing or opening action, thus improving the durability of the contacts.

To the accomplishment of the 'above noted objects the circuit breaker .of the present vinvention comprises the usual contacts, a pair of `cam members, one of which actuates the contacts and a thermostatic latch 'engaging the other cam member to lock it in fixed position, in which a wedging device in the form of `concentric rolls is provided acting on the contact actuating cam member to close the cont-acts against theresista-nce oifered by the locked cammember. By this arrangement it is possible to provide the locked -cammember with a projection for retaining the ywedging ydevice in either of two positions,vwith the contacts closed or opened. The projection may accordingly be constructed to insure a quick closing or opening action for the contacts. This feature of the invention valso conl templates the provision of `resilient'. members for forcing 4the wedging device out' from between the cam members when the locked vcam member is released so that a separate resetting movement td relock that cam member is unnecessary.

These'and otherifeaturesjand advantages-ofthe invention, as `hereinafter described vand claimed, will be apparent .to those skilled inthe vart from the following .detailed specification, taken ,in connection with the accompanying drawings, in which: Y l Y y Fig. l issectional view .of a'trip vfree electrical circuit breaker .embodying the `features of the present invention, showing the parts thereof in positions assumedwith the 'circuitthroughthe breaker closed: Y

Fig. 2Yis =a similar'viewof theparts in positions assumedwith thecircuit opened:

Fig. 3 is asimilar view ofthe operating parts of the breaker shown in lpositions assumedat an intermediate condition, .directly-after .opening the circuit as a result L.of excessive current flow, ibut before the contact actuating wedging device has been forcedoutfrom between the cam members;

Fig, ,4 is a perspective detail view on va somewhat enlarged scale of thecontact actuating cam member; f

Fig. 5 is a similar View of the Vlatch engaging cam member; s

Fig. 6 is a similarview of the wedg-ing rolls;

and

Fig. 7 is plan view ofthe wedging rolls yshowing their manner of contact with Y.the :tWo cam members.

The circuit breaker #illustrated in the ydrawings is of thetrip free type, so called, because of the arrangement of parts, with which it is impossible to hold the contacts closed yunder'conditions of excessive current flowin the circuit-controlled by the breaker. The circuit breaker is manually operated and tripped to-open -the contacts by the action of -a current responsive latch, the action of which -is lto lock the contacts closed or to release nthem for -quick opening `upon eX- cessive currentfflow. A

`The illustrated circuit Abreakercomprises a hollow-rectangular :framefor casing falli of insulating material, "having vone-*end open, "with mounting flanges or'lugs projecting beyond lthe contour r0i' the frame'at the'sides. All ofthe operating parts are inserted Athrough the open end of the frame and are easilyfassembledwithin the frame in operating relation'. `After assembly in theframe the open end thereofisxclosedbya cover or face plate 12.

The operating parts of the `circuit breakerin- "clude contacts M and't, and la swinging -contact actuating'member 't8 composed-of rela-tively wide resilient metallic stripmaterial bent to surround a supporting pivot pin'Z at its :centralportion' andcurved'to vform a cam along one arm disposed vat an angle to the other arm which carries the contact 14. it is acted upon by a manually actuated wedging device 'in the form of a set oi? three concentric rolls 22, 24 and 25, acting against the resistance offered by a second swinging cam member '28 of rigid construction having a yoke portion straddling `the contact actuating cam member I8 Iat the end portions 'of the pivot pin 20. "The pivot pin passes through slots 2l 'in the yoke portion of the member 28 and the sides of the yoke portion are bent toward each other with one side flanged outwardly to provide a relatively narrow central cam arm on the member 23. Near the juncture of the hanged out cam arm of the member 23 an abrupt shoulder 30 is formed engaging the current responsive thermostatic latch, indicated at 32, of bimetallic material formed with a right angle toed out free end. When the latch 32 engages the shoulder 30 the member 28 is locked and the contacts may be closed or opened by forcing the wedging rolls between or out from the cam members.

To force the wedging rolls between or out from the cam members the rolls are mounted on a pin 34 the ends of which are secured in a pair of parallel links 36. The upper ends of the links 3B are pivotally connected to a manually actuated plunger 38 slidably mounted in a sleeve portion of the cover I2. When the plunger is depressed the contacts are closed as in Fig. 1. When the plunger is pulled outwardly the contacts are opened as in Fig. 2.

To enable the wedging rolls to be moved easily between the cam members I8 and 28 the two outer rolls 22 and 24 are formed with a larger diameter than the inside center roll 26. The outside rolls bear individually on the relatively wide surface of the cam member I8. The central cam arm of the member 28 being relatively narrow enters between the rolls 22 and 24 and engages the center roll 28 (see Fig. 7). As the wedging rolls move between the cam members they turn in opposite directions, thus reducing the frictional resistance to that of the rolls on the pin 34. since each roll engages one only of the cam members.

The cam members are yieldingly pressed together so that the wedging rolls will be retained in a definite relation with the cam members or released therefrom, and the cam arm of the member 28 has a projection 39 (see Fig. 5) for this purpose, as well as, to provide a quick closing and opening action for the contacts. For yieldingly pressing the cam members together each cam member is connected with its own resilient means in the form of springs 48 and 42, respectively. The spring 40 is connected to the member I8 and causes the contacts to be opened when the rolls are ineffective to hold them closed. The spring 42 is connected to the cam member 28 and is weaker than the spring 48, so that when the thermostatic latch 32 releases the cam member 28 the resistance offered bv the spring 42 will be overcome by the spring 48 and the contacts will be opened. The cam member 28 will then be forced into an intermediate position. shown in Fig. 3. As soon as the intermediate position is reached the proiection on the cam member 28 engages the roll 26 below the nin 34 urging it outwardly and releasing it from between the cam members, projecting the connected plunger also outwardly. As the plunger moves outwardly the cam member 28 follows the movements of the roll 26 until the roll reaches the position of Fig. 2. When this position of the roll is reached the cam member will be returned to its relocked position with relation to the latch 32. The breaker will then be ready for a new reclosing operation merely by depressing again the plunger 38.

To prevent the cam member I8 from moving too far with the rolls 22 and 24 when the latch engaging cam member 28 no longer offers resistance to keep the contacts closed, the Wedging rolls are guided in their movements and the plunger 38 is mounted to reciprocate between a pair of inwardly projecting ribs 44 on frame I0 and the cam member I8 has a pair of laterally projecting tabs 46. The tabs 46 are so arranged that they engage the ribs 44 when the contacts are opened. The ribs therefore limit the opening movement of the contacts.

The thermostatic latch 32 provided with the toed out free end is arranged to move beneath the shoulder 30 on the cam member 28 when in unheated condition. It is heated by direct passage of current therethrough and when heated to a predetermined temperature it releases the cam member 28 to open the contacts. The latch is mounted for easy adjustment to enable convenient calibration of the circuit breaker for different overload current values in a manner similar tc the latching strip disclosed in United States Letters Patent No. 2,418,537 granted April 8, 1947 upon application of the present inventor. Forthis purpose the frame I0 has a groove 48 running inside its right hand wall and the latch is secured to a terminal plate 5U secured to the inside of the frame by a screw 52 passing through the side wall of the frame. The end of the latch 32 which is secured to the terminal plate 58 is bent in a direction reverse to the main portion of the latch and is disposed within the groove 48. Just below. the point where the latch is secured to the terminal plate vthe plate has a threaded opening to receive an adjusting screw 54 passing loosely through the wall of the iframe. Between the adjusting screw 54 and the securing screw 52 the, terminal plate 50 is weakened by a perforation 56 to facilitate ilexure of the strip resulting from rotation of the adjusting screw 54. The perforation 56 also receives the lower end of the latch 32 v'hen re"easing the cam member 28.

The circuit through the breaker runs from the terminal plate 58, the latch 32, a flexible jumper 58 running through an opening in the cam member I 8 to a point of attachment with the cam member directly above the contact I4, the contact I4, contact I6, and a terminal plate 68 secured to the bottom of the frame kby a screw 62. The use of the flexiblejumper enables the current to pass through the circuit breaker without flowing through the operating parts to any considerable extent.

To enable the cam member 28 to be release from the latch 32 and then to slide freely along the right angle end of the latch without frictional binding, the cam member 28 is shiftable on the pivot pin 20 within the length of the slot 2 I. This arrangement enables the cam member 28 to relatch itself freely also after having been released from the latch, without movement of the latch. After the shoulder 30 on the cam member 28 is raised above the right angle end of the latch it slides along the pivot pin 20 to locked position.

With the construction described the circuit breaker can not be held manually closed and it will reset itself as soon as the rolls are forced out from between the cam members. All that is then necessary to do is to depress again the plunger 38 and the circuit will be reclosed. ,If the conditions causing excess current flow Ihave not been corrected however the circuit will immediately be reopened. In resetting the breaker the plunger 38 to which the rolls are connected is forced manually through the sleeve portion of the cover, indicating the opening of the breaker.

- The lnature #and `scope f of :the i invention having beenindicated and an embodimenty oi the invention '-having lbeen described, what is :claimedis: 1'1.` Atripftree circuitbrealrer .having contacts, a-pair'ofl-camz/membe'rs, vone `of which Iactuates the Acontacts, @a thermostatic latch vengaging fthe other cam member Ito l'ockfit'in 'fixed positionand resilientvmeansifor lactuating `the cam members, inicombinationfw'ith-a wedging device inlthe form of concentrically mountedrolls `acting on said contact actuating cam member 4for closing kthe contacts 2-against the resistance oiiered .by the ldcked vcaniirneniberand said resilient fmea'ns; each of'sai'd concentric rolls engaging .oneonly ofthecammembers.

i Tv2. A ftripfree-circuit breaker having contacts, a pair of swinging foam membershavinga,comn mon A pivot,;one 'oir-which cam members actuates thecontacts, amanuallyY operatedswedging device iorffswinging'ithe cammembers away ,from each otherfabout said pivot :and resilient `means for actuating the cam members together, in coinbinationwith :a `thermostatic latch for locking the .other yof said camfmembers in position itc causer-the contacts toibe closed by the wedging device. aganstfthe resistance offered bythe locked cam member-,and rthe`resilient means.

93. A 'trip :free circuit 'breaker having contacts, apainof swinging Acam members having a `common ipivot, ,one otwhich cammernbers actuates thexcontacts,r afmanually actuated wedging device for 'swinging fthe `cam :members :awayfrom each other .about said pivotflandzresilent '.means vfor actuating :the contact :actuating Acamfir'ito circuit openingfposition, :in :combinationxwith 1a lthermostaticdatch engaging the othercam member .to

lock :it in ,position :where fthe .contacts :may be y closed by `the wedg'ing device against `the :resistance offered by the locked cam frmember, zsaid latch engaging'icamimember having a projection 'to retain the wedging device between the cam members but to releasethe wedging device from between the cam members when the latch engage ing cam member is unlocked and is swung to one side, and second resilientmeans for urging the wedging device out from between the cam members zwhen released by the projection and for urging fthe latch engaging cam member into A'relockedlposition. Q*

"-4., A.trip "free .circuit .breaker 'having contacts,

a pair of cam members, one of which actuates the'y contacts, a thermostatic latch engaging the other ycam member to lock it is xed position and resilient means for actuating the cam members together, in combination with a wedging device acting on said contact actuating member for closing the contacts against the resistance oiered by the locked cam member and said resilient means, one of the cam members having a surface of extended'widtengaging the wedging rdevice and the other cam-member having a relatively narrow surface engaging the wedging device and the wedging devicecomprising three concentric rolls, two of which are spaced apart *and act on the cam member of extended width and the remaining one of which acts on the cam member having the narrow surface. i

k 5. A trip free circuit breaker having contacts, a pair of cam members, one of which actuates the contacts, a thermostatic latch engaging the other cam member to lock it in fixed position and resllient means for actuating the cam members tcgether, in combination with a wedging device acting between the cam members for closing the contacts against the resistance offered by the a pai'rof cammembers, one-of which .actuates the contacts, athermostatic latch engaging lthe other cam memberto lock itin .a iixedfposition and resilient means for .actuating `the cam finembersltogether, in .combination .with a 'wedging device acting between the cam members .for closing the .contactsfiagainst the resistance .offered bythe locked cam member land the resilient means, the contact .actuating cam ymember vhaving a surface of extended width engaging the wedgingdevi'ce, the locked :cam member having a relatively-nar row ,surface vengaging the wedging rdevice and the .wedging ydevice comprising three `concentric rolls, the .two outside ones of which act .on the" contaotactuating cam .member and .the insideone of which .acts :on the locked cam `:member while rotatingrin `a direction opposite to that of the outsidelrolls. v

7. A trip free circuit breaker having contacts, a `pair of cam members, one of 'which actuates the contacts, a thermostatic latch engaging the other cam member to lock 'it inixed'position and resilient means for actuating vthe cam yz-menilcers together, in .combinationwith ,a wedgin'g device acting between Ithe cam members for closing the contacts ,against the resistance offered by the locked cam member and the resilient means,the contact actuating cam member. having Aauf-surface `of :extended width lengaging .thewedging device; the v'locked cam member 'having 'a' relativelytn'arrow surface engaging the wedgingdevice-.and the actingl between the cam members and being guided between the ribs and a plunger mounted for reciprocation between said ribs, one of the cam members having laterally projecting tabs arranged to engage the edges of said ribs to'limit the movement of the tab bearing cam member toward the other cam member under the action of the resilient means when the wedging device is moved from between them.

9. A trip free circuit breaker having contacts, a pair of cam members, one of which actuates the contacts, a pivot about whichboth cam members swing, a thermostatic latch engaging the other cam member to lock it in fixed position and resilient means for actuating the cam members rtogether, in combination with a wedging device acting between the cam members for closing the contacts against the resistance offered rby the locked cam member and the resilient means, the

7 contact actuating cam member itself also being composed of resilient material and the locked cam member being relatively rigid.

10. A trip free circuit breaker having contacts, a pair of cam members, one of which actuates the contacts, a thermostatic latch engaging the other cam member to lock it in Xed' position and resilient means for actuating the cam members together, in combination with a set of wedging rolls acting between the cam members for closing the contacts against the resistance offered by the locked cam member and the resilient means, the contact actuating cam member itself also being composed of relatively wide resilient material against which two of the rolls act and the locked cam member being composed of relatively narrow rigid material against which acts one of the rolls disposed between the others. l

1l. A trip free circuit breaker having contacts, a pair of cam members, one of'which actuates the contacts, a thermostatic latch engaging the other cam member to lock it in fixed position and resilient means for actuating the cam members together, in combination with a set of concentric wedging rolls acting between the cam members for closing the contacts against the resistance offered by the locked cam member and the resilient means, the contact actuating cam member itself being composed of relatively wide material against which two of the rolls act and the locked cam member being in the form of a yoke with a central projecting cam arm against the edge of which acts a third one of the rolls disposed between the said two rolls acting on the contact actuating cam member. v y

12. A trip free circuit breaker having contacts, a pair oi cam members, one of which actuates the contacts, a thermostatic latch engaging the other cam member to lock it in xed position and resilient means for actuating the cam memberstogether, in combination with a set of concentric wedging rolls acting between the cam members for closing the contacts against the resistance oiered by the locked cam member and the resilient means, the locked cam member having a slot and fulcrum pivot pin mounting alined with the thermostatic latch to enable relatching without movement of the latch.

13. A trip free circuit breakerlhaving contacts, a pair of swinging cam members having a common pivot, one of which cam members actuates the contacts and a manuallyactuated wedging device for swinging the cam membersaway 'from each other about said pivot, in combination with a current responsive latch engaging the other cam member to lock it in position where the contacts may be closed by the wedging device against the resistance offered by the locked cam member, said latch engaging cam member having a projection to retain the wedging device between the cam members but to release the wedging device when the latch engaging cam member is unlocked and is swung to one side, resilient means for urging the wedging device out from between the cam members when released by the projection and other resilient means for returning the latch engaging cam member to locked position.

14. A trip free circuit breaker having contacts, a pair of swinging cam membershaving a common pivot, one of which cam members actuates the contacts and a manually actuated wedging device for swinging the cam members away from each other about said pivot. in combination with a current responsive latch engaging the other cam member to lock it in position where the contacts may be closed against the resistance oiered by the locked cam member, said latch engaging cam member having a projection to retain the wedging device between the cam members but to release the wedging device when the latch engaging cam member is unlocked and is swung to one side, and two springs, one of which is connected to the contact actuating cam member to open the contacts and the other of which is connected to the latch engaging cam member to press the wedging device out from between the cam members after the contacts are opened and to turn the latch engaging cam member to locked position after releasing the wedging device.

MORRIS B. WOOD.

REFERENCES CITED The following references lare of record in the file of this patent:

UNITED STATES PATENTS 2,496,072V Taylor Jan. 31, 1950 

